Concussions are typically associated with grossly normal structural neuroimaging studies. [1]In other words, unlike other injuries, concussions are usually injuries no one sees and, contrary to popular belief, don't show up on most magnetic resonance imaging (MRI) exams or CT scans.

Because conventionial neuroimaging contributes little to concussion evaluation and management, [1,4] the 4th international consensus statement on sport-related concussion, [1] the 2013 American Academy of Neurology concusson guidelines,[2 the 2013 American Medical Society for Sports Medicine position statement on concussion in sport, [3]and the American Academy of Pediatric's 2010 Clinical Report on Sport-Related Concussion in Children and Adolescents [4]all state that conventional CT or MRI scans of the brain are not needed or recommended in the vast majority of concussions..

All acknowledge, however, that CT or MRI are valuable and should be used when there is or has been:

Whenever there is a suspicion of an intracranial structural injury [1,4]

Loss of consciousness (LOC) for more than a minute [1-3]or 30 seconds [4](remember: a concussions may or may not involve LOC, with 90% of all concussions occurring without LOC);

Speech or language difficulties such as aphasia or dysarthria (impaired speech and language skills), poor enunciation, poor understanding of speech, impaired writing,impaired ability to read or to understand writing, inability to name objects (anomia)[4]

Note: Normal neuroimaging results in the acute phase of injury may not rule out a chronic subdural hematoma or subsequent neurobehavioral dysfunction. [4]

CT or MRI?

A CT scan is the test of choice to evaluate for the four types of intracranial hemorrhage (subdural, epidural, intracerebral, or subarachnoid) bleeding in the brain, swelling of the brain during the first 24 to 48 hours after injury, or to detect a skull fracture[4] because it is faster, more cost-effective, and easier to perform than an MRI. [2,4] No test, however, currently available is sensitive and specific enough to diagnose all intracranial injuries.

An MRI may be more appropriate if imaging is needed 48 hours or longer after an injury [4] to evaluate persistent or worsening symptoms or where there is a concern for underlying pre-existing conditions (eg. headache or seizure disorder, arteriovenous malformation, Chiari malformation, etc.) and is best coordinated through your child's primary care physician or the specialist evaluating your child. [4] Because MRI is viewed as superior in detecting traumatic lesions of the brain, and does not expose patients to radiation, [6] a 2011 study [5] recommends its use for assessing traumatic sport-related brain injuries, especially after the acute period.

Note of caution

The use of CT scans in diagnosing concussion is surprisingly common among neurologists. A 2011 study [5] found the CT rate among neurologists at 72.2%, a rate the study's author and MomsTEAM concussion expert, William P. Meehan, III, MD, said was "probably higher than it needs to be." No wonder, then, that the new American Academy of Neurology guidelines state in no uncertain terms that "CT imaging should not be used to diagnose [sport-related concussion]." [2]

In addition to being ineffective (and expensive), there is another reason for fewer CTs: A 2012 study reported in the British medical journal, The Lancet[6]found that children and young adults scanned multiple times by CT have a small
increased risk of leukemia and brain tumors in the decade following
their first scan. A 2013 study[7]suggests that reducing the highest 25% of radiation doses could prevent 43% of those cancers.

The bottom line: parents should make sure a CT scan is really necessary in treatment of their child after head injury.

1. McCrory P, et al. Concussion
statement on concussion in sport: the 4th International Conference on
Concussion in Sport held in Zurich, November 2012, Br J Sports Med 2013;47:250-258.